Thermostatic switch



Dec. 4, 1962 H. D. EPSTEIN 3,067,305

THERMOSTATIC SWITCH Filed Nov. 10, 1960 2 Sheets-Sheet 2 FIG. 7. 4/ 31 Jib-m nited States atent O 3,067,395 THERMOSTATIC SWITCH I Henry David Epstein, Cambridge, Mass, assignor to Texas Instruments incorporated, Dallas, Tern, a corporation of Delaware Filed Nov. 10, 1960, Ser. No. 71,861 27 Claims. (Cl. 206-138) This invention relates to thermostatic switches, and more particularly to thermostatic switches in which novel means are provided for adjusting the pressure between the electrical contacts thereof.

This application is a continuation-in-part of my United States patent application Serial No. 812,984, filed May 13, 1959, for Thermostatic Switch, now abandoned.

Among the several objects of the invention may be noted the provision of thermostatic switches of such construction that the pressure between contacts may be readily adjusted; the provision of switches of this class which may be readily assembled and conveniently calibrated during assembly; the provision of switches of the class described adaptable to use in vibratory surroundings; and the provision of such switches which are simple in construction and reliable in operation. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comp-rises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of which will be indicated in the following claims.

In the accompanying drawings, in which two of various possible embodiments of the invention are illustrated,

FIG. 1 is an axial section of one form of a thermostatic switch made according to the present invention;

FIG. 2 is a cross section taken on line 22 of RIG. 1;

FIG. 3 is a fragmentary horizontal section taken on line 33 of FIG. 1;

FIG. 4 is a cross section taken on line 4iof FIG. 1;

FIG. 5 is a cross section similar to FIG. 2 but showing the cover of the device rotated 180 from the position shown in FIG. 2;

FIG. 6 is a fragmentary cross section, parts being shown in elevation, illustrating an alternative construction;

FIG. 7 is a view similar to FIG. 1, showing another form of looped control finger;

FIG. 8 is a view similar to FIG. 7, showing another means of adjustment;

FIG. 9 is a view similar to FIG. 8, showing another form of the casing of the device; and

FIGS. 10, 11 and 12 are cross sections taken on lines 101tl, 11-41 and 12-42 of FIGS. 7, 8 and 9, respectively.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawmgs.

Referring now to the drawings, the invention constitutes a thermostatic switch generally designated 1. The switch comprises a cup-shaped switch housing or frame 3 of cylindrical outside shape. The housing 3, which is molded of a nonconductive material, preferably of a suitable plastic, has a closed bottom 5, elongate side elements or walls and an open end 7 adapted to receive a head or cover 17. Within the housing 3 is a recess 9 which is in the form of an oblique cone. With the exception of one side element 4 of the cone, all other elements of its internal surface taper inward from the outer end 7 of housing 3 toward the bottom 5 to form an eccentric cam portion 41. The outer end 11 of recess 9 is defined by a circle, and the inner end 13 of recess 9 is defined by a circle of smaller diameter, the axis of the inner circle being ofiset laterally from the "ice axis of the outer circle so that the inner and outer ends 11 and 13, respectively, of recess 9 are eccentrically related to each other.

Received within recess 9 is an assembly generally designated 15. Assembly 15 comprises a nonconductive cover or closure 17 of suitable plastic material for the open end 7 of housing 3. Extending inward into recess 9 through openings 18 in the closure 17 are a conductive rigid strip 19 and a conductive flexible spring arm 21. These also extend outward to form outside line terminals 23 and 25, respectively, separated from each other by an insulating tongue 27 forming part of the cover 17 between openings 18. Tongue 27 extends inward through closure 17 into recess 9 and also extends outward. Sandwiched between strip 19 and tongue 27 is a resilient thermostatic element 29. Strip 19, arm 21, tongue 27 and thermostatic element 29 are fastened together by a rivet 31 having a shouldered insulating washer 33 at its lower end to prevent conductive electrical engagement between arm 21 and rivet 31. Members 21 and 29 are of strip form and adapted to flex in a common plane. In this sense they are coplanar.

Spring arm 21 is preferably composed of a beryllium copper alloy and carries electrical contact 35 welded thereto as indicated at 37. Extending from the end of arm 21 and integral therewith is a finger 39 in the shape of a springy loop. The outer end 40 of finger 39 is formed for relative rotary sliding engagement with internal cam surface portion 41 of recess 9.

The thermostatic element 29 is preferably made of flexible birnetal, including a dished or dimpled portion 43 for imparting snap action thereto in response to temperature changes, as indicated by the dotted lines. The rigid strip 19 backs strip 29 from its anchor point at 3 1 to the dimple 43. Thermostatic element 29 carries electrical contact 45 for engagement with contact 35. It will be noted that thermosatic element 29 is in electrical connection with strip 19. If contact 45 is pushed a small amount from its solid-line position shown in FIG. 1 toward its dotted-line position, the end of strip 19 backs the dimple 43 to efiect a calibration of temperature at which the dimple will snap to reverse its curvature to withdraw contact 45 from contact 35.

The thermostatic switch of the present invention may be conveniently calibrated during assembly. In practice, assembly 15 is inserted into recess 9 of the housing 3 through the open end 7 thereof. As shown in FIG. 1, this brings outer end 40 of finger 39 into engagement with surface portion 41 of recess 9 by reason of the eccentricity of inner end 13 of recess 9 relative to the outer end 11. The bearing engagement of outer end 40 of finger 39 on surface 41 determines the position of contact 35. It will also be observed that the position of contact 35 with respect to strip 19 will determine the amount of effective so-called pull-in of the snap-acting element 29, and that for any given position of assembly 15 within recess 9 there will be a certain amount of disc pull-in. It is known in the art that the snap temperature of an inherently snap-acting dished, dimpled or like device may be adjusted by mechanically reducing the amount of curvature of the dished portion, as by pulling or forcing the center of the dished portion toward the plane of the periphery of the dished portion. This pull-in determines the temperature at which the dished or dimpled portion 43 of thermostatic element 29 will snap from the so-called cold position shown in solid lines in FIG. 1 to the flexed position suggested in dotted lines in FIG. 1. Rotation of the closure element 17 in the recess 9 will tend to move contact 35 toward the fixed strip 19 and thus to force the dimpled portion 43 against the end of strip 19. This pulls in the dished portion and changes the temperature at which the element will snap.

FIG. 2 illustrates the rotary position of assembly 15 within recess 9 at which the minimum pull-in contact pressure between contacts 35 and 45, respectively, will occur by reason of the engagement of outer end 40 of finger 39 with the high surface portion 41 of recess 9.

1G. shows the position assumed by contacts 35 and 45 upon rotating the housing 3 180 relative to the assembly In this FIG. 5 position, maximum contact pressure between contacts 335 and 45, respectively, will occur by reason of the return-spring action of arm 21. This raises the pull-in pressure between contacts and 45. Thus, by rotating assembly 15 in either a clockwise or counterclockwise direction so as to move outer end of finger 39 in sliding engagement with surface portion 41 of recess 9, various degrees of contact pressure between contacts 35 and may be conveniently obtained. In this manner, the thermostatic switch of the invention may be readily calibrated for operation at any desired temperature. After the switch has been calibrated at the desired temperature, the assembly 15 is sealed into housing 3 by hot-staking the cylindrical end of housing 3 to the cylindrical closure 17, as indicated at 47.

The purpose of the extension or loop 39 is to cause the spring-biased movement of arm 21 to drive the loop against the eccentric cam portion 6 and to drive contact 35 toward contact &5. This loop 39 also provides additional springiness for the mounting of contact 35, since the loop is formed of the same spring material as forms arm 21. It will be apparent that, by slopingly extending the cam portion 41 from its region of contact with loop 39 toward the head end of the cup-shaped housing, the operation of the assembly is made easier because of the absence of any interfering internal shoulders, steps or the like.

In FIG. 6 is shown an alternative construction for obtaining a rotary connection between the assembly 15 and the housing 3. In this drawing the housing 3 is shown in section and the assembly 15 partly in elevation and partly in section. The end or" the housing 3 is internally threaded, as shown at 4-9. The cover portion 17 of the assembly 15 is also threaded as shown at 51 for cooperation with the threads 49, being also provided with an underlying groove 53. Thus prior to any heat staking, threads 51 and 49 are threaded together and the appropriate rotary adjustment made. After the adjustment has been accomplished, heat staking such as shown, for example, at a in FIG. 6 is brought about, which interlocks material at the end of the housing 3 with the groove 53 and maintains the previously threaded adjustment. It will be understood that staking can be applied at additional points, or all around groove 53. An unstaked condition is illustrated at b in FIG. 6 in order to illustrate the conditions that exist all around groove 53 before any staking and during rotary adjustment. This threaded form of rotary adjustable connection between housing 3 and the assembly 15 has the advantage that external means for holding them are not required during the adjusting operation.

In FIG. 7 is shown a form of the invention which is like that in FIG. 1 to the extent shown by the corresponding reference numerals in FIG. 7, and to that extent repetition of description will not be necessary. In this modification, the form of the loop 39' (analogous to loop 39 in FIG. 1) is modified. The end 4i) of loop 39' springingly engages the cam surface 41. Its curved portion extending from the spring end it? is so formed as springingly to engage the opposite side of the conical inside of housing 3. Thus the arm 21 is converted from the cantilever type shown in FIG. 1 to a double-supported beam type, its end supports being on the closures 17 and at the contact portion fill. This arrangement is advantageous in those cases in which the switch is mounted on vibrating equipment, since the springing radial pres sure at points 40 and 6.; guards against any vibration or" contact 35 due to cantilever mounting as in FIG. 1. Contact 45, being on the end of member 29 containing the dimple 43 and engaging contact 35, likewise does not respond to vibration as a cantilever. Except for the double-supporting contacts obtained at points 40' and 61, the operation of the FIG. 7 form of the invention is like that described in connection with the form shown in FIG. 1.

In FIG. 8 is shown another form of the invention like that shown in FIG. 7. insofar as its form is identical -ewith, like numerals have been employed. The point of structural departure in this PEG. 8 case concerns the type of motion employed for adjustment. In this form the housing 3 is formed at its open end with an elongate cylindrical sleeve 63. At 17' is shown a closure of cylindrical disc form for supporting the assembly 15. Th' closure is both rotatably and axially movable in the sleeve as prior to hot-staking. The assembly 15, including the closure 17', prior to assembly is rotated relative to the housing 3, so that point of the loop 39 engages the cam surface 41. The closure 17' is then pushed into the sleeve 61 until a desired adjustment of the position of the contact 35' is obtained, whereupon the hot staking shown at is illustrated. It will be understood that, as in the FIG. 7 form of the invention, the loop is sprung inward from its free position such L77 that at any adjusted position within the housing 3 there is spring-holding pressure between points 4% and 61, and the opposite parts of housing 3. This form of the invention has the advantages of the FIG. 7 form, insofar as is concerned the beam characteristics of the arm 21. It also has the further advantage of contact adjustment by axial sliding movement of the assembly 15 in the housing 3. Furthermore, additional adjustment may be made by rotation of the assembly at any given point of axial adjustment. This considerably increases the range of adjustment available.

In FIG. 9 is shown another form of the invention comprising a switch housing 67, composed of metal which is both heatand electrically-conductive. Its interior is constituted by an eccentric conical form providing a cam surface 41. inside this housing 57 is a switch assembly 15 which is like that described in connection with a sembly 15, like numerals designating like parts. This assembly 15', however, differs from assembly 15 in that the arm 21 is deprived of its line terminal such as shown at 25 in FIGS. 1, 7 and 8, leaving it with only the line terminal 23. The assembly 15' is again carried on an insulating closure disc 69 which is rotatable and slidable in sleeve 63' of the housing 67. Thus the assembly 15 may be introduced in the housing 67 by introducing the cover 69 in the sleeve 63 and making the adjustments such as heretofore described in connection with FIG. 8. Staking then is effected at 65.

This form of the invention has the advantage that when the contacts 45 and 35 are engaged (as shown), a circuit may be closed through terminal 23 and casing 67, to which an appropriate soldered, welded or like terminal connection may be made at any point. It also has the advantage that heat is more rapidly conducted through the metal housing 67 to the thermostatic member 29', for more rapid thermostatic response.

In view of the above, it will be seen that the several Objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter continued in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a imiting sense.

i claim:

1. A thermostatic switch comprising a hollow housing having elonga e si e elements and an opening at one end in which is an insulating cover, means adapted to lock together the housing and cover, said opening and cover being formed for adjusting movements of the cover prior to locking, the elongate side elements of the housing defining a camming surface, a thermostatic switch carried on the cover and Comprising a pair of electrical contacts engageable and disengageable with each other, a thermostatic member carrying one of said contacts, and a bendable conductive arm carrying the other of said contacts and having at least one point of engagement with said camming surface.

2. A thermostatic switch comprising a hollow housing having an opening at one end in which is an insulating cover, means adapted to lock together the housing and cover, said opening and cover being formed for adjusting movements of the cover prior to locking, the hollow portion of the housing defining a camming surface, a thermostatic switch carried on the cover and comprising a pair of electrical contacts enga-geable and disengageable with each other, a thermostatic member carrying one of said contacts, a bendable conductive arm carrying the other of said contacts and having a springy loop portion at its end, said loop portion having at least two opposed points of engagement with said camming surface.

3. A thermostatic switch comprising a hollow housing having elongate side elements and an opening at one end in which is an insulating cover, means adapted to lock together the housing and cover, said opening and cover being formed for adjusting movements of the cover prior to locking, the elongate side elements defining a camming surface within the hollow portion of the housing, a thermostatic switch carried on the cover and comprising a pair of electrical contacts in the housing engageable and disengageable with each other, a thermostatic member carrying one of said contacts, a substantially rigid conductive member carried by the cover and conductively connected with said thermostatic member, said conductive member extending exteriorly from the cover to form a terminal, and a springy conductive arm carrying the other of said contacts and having at least one point of engagement with said ca-mming surface.

4. A thermostatic switch according to claim 3, wherein said thermostatic member is a thermostatic strip including a snap-acting portion and wherein said substantially rigid conductive member includes a part near said snapacting portion for pull-in elfect on the same.

5. A thermostatic switch according to claim 3, wherein said housing is composed of electrically conductive material thereby to form another terminal.

6. A thermostatic switch according to claim 3, wherein said housing is composed of electrically insulating material and said conductive arm includes an electrically conductive exterior extension from the cover to form another terminal.

7. A thermostatic switch comprising a hollow housing having an opening at one end in which is an insulating cover, means adapted to lock together the housing and cover, said opening and cover being formed for adjusting movements of the cover prior to locking, the hollow portion of the housing defining a camming surface, a thermostatic switch carried on the cover and comprising a pair of electrical contacts in the housing engageable and disengageable with each other, a thermostatic member carrying one of said contacts, a substantially rigid conductive member carried by the cover and connected with said thermostatic member and forming a backing for the same, said conductive member extending from the cover to form a terminal, and a bendable conductive arm carrying the other of said contacts and having a sprin-gy loop portion at its end, said loop portion having at least two opposed points of engagement with said camming surface.

8. A thermostatic switch according to claim 7, wherein said thermostatic member is a thermostatic strip ineluding a snap-acting portion and wherein said substan tially rigid conductive member includes a backing part near said snap-acting portion for pull-in eliect on the same.

9. A thermostatic switch comprising a hollow housing closed at one end and having a cylindrical opening at the other end in which is a cylindrical insulating cover, means locking together the housing and cover in one of the various axial and rotary optional positions between the cylindrical opening and cover, a recess in the housing extending inward from said opening, said recess de fining a cam portion extending both axially and peripherally, a switch assembly on the cover and extending into said recess, a pair of electrical contacts in said assembly engageable and disengageable with each other, a thermostatic member carrying one of said contacts, and a bendable conductive arm carrying the other of said contacts and having a springy loop at its end and having two opposite points of engagement with said cam portion.

10. A thermostatic switch according to claim 9, wherein said housing is composed of electrically insulating material, and including conductive terminals carried externally on the cover and extending inward therethrough into electrical connection with said thermostatic member and bendable arm, respectively.

ll. A thermostatic switch according to claim 9, wherein said housing is composed of electrically conductive material, and including a conductive terminal carried externally on the cover and extending inward therethrough into electrical connection with said thermostatic member.

12. A thermostatic switch construction comprising a tubular housing having a recess therein shaped as an axially and peripherally extending cam, said cam being formed by the elongate side Walls of said tubular housing, said housing having a cylindrical opening leading into said recess wherein is located a cylindrical insulating closure locked thereto, an assembly carried by said closure, said assembly including opposite conductive arms extending inward from the closure, one of which is terminated by a springly loop engageable with said cam, and a thermostatic strip in conductive relation to the other arm and having a snap-acting portion adjacent the end of said other arm, said first arm carrying a contact, said thermostatic strip also carrying a contact engageable therewith and located beyond said snap-acting portion.

13. A thermostatic switch construction comprising a tubular housing having a recess therein shaped as an axially and peripherally extending cam, said housing having a cylindrical opening leading into said recess wherein is located a cylindrical insulating closure locked thereto, an assembly carried by said closure, said assembly including opposite conductive arms extending through the closure, said arms forming exterior terminals and one of which is interiorly terminated by a springy loop engageable with said cam at two opposed points of pressure, a thermostatic strip in conductive relation to the other arm and having a snap-acting portion adiacent the end of said other arm, said first arm carrying a contact, said thermostatic strip also carrying a contact engageable therewith and located beyond said snap-acting portion.

14. A thermostatic switch comprising an assembly having a circularly disposed insulating support, a movable thermostatic element and a movable spring element mounted thereon, said elements respectively carrying contacts which are springingly pressure-engaged by the spring element, a frame having a circularly disposed portion adapted for rotary engagement with said circularly disposed support and having an eccentric cam portion engageable with said spring element adapted to vary the contact pressure upon rotation of the circularly disposed portion of the frame on said circularly disposed support.

15. A thermostatic switch according to claim 14, wherespe /33cc 7 in frame is in the form of an enclosing housing for said elements and forming said eccentric cam portion on its insi e, and wherein said support is in the form of a cover for the housing through which extend said elements to form outside terminals.

16. A thermostatic switch according to claim 14-, where in said elements are in strip form extending substantially parallel to another from said support, the other end portions of which are movable and carry contacts, said movable end portion of the spring element having an extension formed crosswise of the movable end of the thermostatic clement, whereby the direction of movement of the spring element which forces its contact toward the other contact also moves said extension against said cam portion.

17. A thermostatic switch according to claim 16, wherein the thermostatic element is snap acting and said exension is in the form of a resilient loop engaging said cam portion at two opposite points.

18. A thermostatic switch comprising an assembly including an enclosing head forming a circular support for a strip-type thermostatic element anchored thereon and a strip-type spring element adjacently anchored thereon, said elements extending adjacent one another toward unanchored ends and respectively carrying adjacent said ends contacts Wh' it are springingly pressure-engaged by the spring element, an enclosing cup-shaped housing having a circular open end portion rotatably engaging said head support and having an inner eccentric cam portion engageaole with said spring element adapted to vary the contact pressure upon rotation of the circular portion of the housing on said circular support.

19. A thermostatic switch according to claim 18, wherein said thermostatic element for snap action has a dimplcd portion adjacent its contact and is backed by a rigid strip extending from its anchor to its dimpled portion.

20. A thrmostatic switch comprising a housing closed at one end and open at the other end and having elongate side elements, a recess in the housing, and an assembly within said recess adapted to be received through said open end of the housin and comprising a pair of electrical contacts engageable and disengageable with each other and a thermostatic member carrying one of said contacts, said recess having an internal cam surfce portion formed by said side elements slidingly engageable by a portion of said assembly, whereb upon movement of the assemly the pressure between said contacts may be varied.

21. A thermostatic switch comprising a cup-shaped housing having a closed end and an open end and forming a recess, an assembly extending within said recess adapted to be received through said open end of the housing and comprising a pair of electrical contacts engageable and disengageable with each other, a thermostatic member carrying one of said contacts and a springy conductive member carrying the other of said contacts, said recess having axially sloping side walls forming a cam adapted slidingly to engage a portion of said conductive member upon relative movement of the assembly in the housing thereb to vary the pressure between said contacts.

22. A thermostatic switch comprising a cup-shaped housing closed at one end and open at the other end, a recess in the housing, the ends of said recess being defined by circles of different sizes, the smaller of which circles is adjacent said closed end and the larger of which is adjacent the open end, the axis of the smaller circle being eccentric with respect to the axis of the larger circle so that one end of said recess is eccentric relative to the other end thereof, an assembly within said recess received through said open end of the housing and comprising a pair of electrical contacts engageable and disengageable with each other, a thermostatic member carrying one of said contacts, a conductive arm carrying the other of said contacts and having an integral loop at one end thereof, and an insulating member sandwiched between and fastened to said thermostatic member said arm,

said loop being in sliding engagement with an internal cam surface portion of said recess whereby movement of said assembly will vary the pressure between said contZZC'LS.

23. A thermostatic switch comprising a cylindrical housing closed at one end and having an opening at the other end, a recess in the housing, each end of said recess being defined by a circle of different size than that of the other, the larger forming said opening, the axis of one circle being laterally offset from the axis of the other circle so that one end of said recess is eccentric relative to the other end thereof, an assembly within said recess adapted to be received through said open end of the housing and comprising a circular cover fitting said circular opening for rotation therein and a pair of electrical contacts engageable and disengageable with each other, a thermostatic member carrying one of said contacts, a conductive arm carrying the other of said contacts and having an integral loop at one end thereof, a pair of line terminals adapted to extend out of said recess through said cover, and an insulating member forming part of said cover and being located between said thermostatic member and said arm, said cover having openings through which said line terminals extend, the outer end of said loo-p being in sliding engagement with an eccentric portion of said recess whereby relative rotation of said cover in said opening varies the pressure between said contacts, said housing and cover being adapted to be locked together after rotation.

24. A thermostatic switch comprising an assembly having a circular support for a flexible thermostatic strip element and an adjacent flexible spring strip element mounted thereon for substantially coplanar flexing movements, said elements respectively having free end portions carrying contacts which are springingly pressureen aged by the spring element, the spring strip element having an endwise loop lying in the plane of said strips and extending across the thermostatic strip, a frame having a circular portion adapted for engagement with said support and having side walls forming a cam portion engageable with the end of said loop.

25. A thermostatic switch construction comprising an assembly including adjacent flexible spring and thermostatic members one end of each of which is anchored with respect to the other, a cover forming the anchor therefor, the other ends thereof being free and adapted for coplanar flexing, said free ends carrying movable contacts adapted to be engaged and disengaged, the spring member being adapted to bias said contacts together, a housing for said spring and thermostatic members having a threaded bearing arrangement with respect to said cover, an internal cam formed by the walls of the housing adjacent the free ends of said members, said spring member having at its free end a finger extending crosswise with respect to the free end of the thermostatic member and engageable interiorly with said cam.

26. A thermostatic switch construction comprising an assembly including adjacent flexible spring and thermostatic members one end of each of which is adjacently anchored with respect to the other, a cover forming the anchor therefor, the other ends thereof being free and adapted for coplanar flexing, said free ends carrying movable contacts adapted to be engaged and disengaged, the spring member being adapted to bias said contacts together, a housing having a transversely cylindrical bearing arrangement with respect tosaid cover near said anchored ends, an internal cam supported by the housing adjacent the free ends of said members, said spring member having at its free end a loop extending crosswise with respect to the free end of the thermostatic member and engageable at two opposite points interiorly with said cam.

27. A thermostatic switch construction comprising a housing having a recess therein shaped as an axially and peripherally extending camming surface, said housing having a cylindrical opening leading into said recess wherein is located a cylindrical closure rotatably and axially movable with respect to said housing, a switch comprising a pair of contacts engageable and disengageable with each other, a thermostatic element mounted on said closure carrying one of said contacts, a spring member mounted on said closure carrying the other of said contacts, said spring member being adapted to spring bias said contacts together and having at least one point of both rotational and axial movement of said closure with respect to said housing said spring bias may be varied.

References Cited in the file of this patent engagement with said camming surface, whereby upon 10 2,925,599

UNITED STATES PATENTS Lord at al. Nov. 2, Brock June 17, Ulanet Feb. 12, Moksu Jan. 21, Wells Feb. 16, 

